Specifically Gates gave funding to David Keith from the University of Calgary, and Ken Caldeira from the Carnegie Institution for Science, for projects that looked at planet-cooling technologies, says the Citizen. Those researchers in turn gave $300,000 to Armand Neukermanns, a researcher involved with the San Francisco-based Silver Lining Project, a program which studies how tiny droplets of seawater sprayed over the ocean could “brighten” clouds and reflect sunlight back into space.

The Silver Lining Project plans to do the world’s first cloud brightening pilot test, and as the Times reports, such a trial would use 10 ships, each carrying machines that can convert seawater into tiny particles that can blown up to the cloud level in the atmosphere. The ships would spray the mist across 3,800 square miles of ocean.

As far as geoengineering experiments — the intentional, large-scale modification of the global environment — go, this one is relatively benign given it doesn’t add chemicals or genetically modify the environment (see Top 10 Most Controversial Ways to Save the Planet). But there could be unintended consequences of changing the makeup of ocean-covering clouds, like weather fluctuations.

For Gates, the reaction to his geoengineering investment is also a good reminder of the need to carefully track investments — with billions at his disposal, his funding could easily trickle down and land somewhere unintended. But Gates clearly is ready to take risks with his greentech support. At the recent TED conference, where Gates first spoke of backing energy innovation, he emphasized that the world needs to find “energy miracles” to reach zero carbon emissions, and requires thousands of companies delivering innovation on clean power including solar thermal, solar PV, batteries and nuclear. And unlike with information technology, there is a deadline for the innovation in clean power, said Gates.